An overhead cam valve train system may include a cam, valve, hydraulic lash adjuster and a rocker arm. The rocker arm, which may be also called the roller finger follower, may include a bearing or slider pad contacting the cam. The rocker arm may also include a surface in contact with the valve, as well as a surface that is in contact with a ball plunger of the hydraulic lash adjuster. As the cam rotates, the rocker arm may translate the circular motion from the cam into linear motion, where the linear motion may be communicated to the hydraulic lash adjuster and the valve. The valve may be actuated in a linear motion in an effort to allow air in and out of a cylinder. A compression spring may be added to the valve to keep the rocker arm in permanent contact with the valve, cam, and hydraulic lash adjuster.
Some types of valve train systems may be used in high powered multi-cylinder internal combustion engines. High powered engines may be used in applications where quick acceleration or heavy towing capacity is needed. However, if the high powered engine is used in an application requiring less power, the extra output from the engine may be wasted. To improve efficiency and reduce waste, these high powered engines may be designed to include cylinder deactivation, where less than all of the cylinders may be activated in at least some lower power operating conditions. During cylinder deactivation, fuel and air may not be delivered to some of the cylinders. In one approach, air may be suppressed to an inactive cylinder by closing the valve corresponding with the inactive cylinder. This may be accomplished by including a type of partially collapsible hydraulic lash adjuster with the inactive cylinder, where the collapsible hydraulic lash adjuster may absorb the linear motion of the rocker arm. That is, during cylinder deactivation the collapsible hydraulic lash adjuster may absorb the linear movement of the rocker arm, and as a result the valve will remain closed.
In some situations, the rocker arm may disengage from the ball plunger of the hydraulic lash adjuster during cylinder deactivation, which may cause damage to the valve train system. There are several approaches that may be used to limit separation between the ball plunger of the hydraulic lash adjuster and the rocker arm. In one approach, a clip is added to the hydraulic lash adjuster. The clip may engage with the ball plunger of the hydraulic lash adjuster, Because the clip is a separate part, there may be extra cost associated with adding the clip to the existing rocker arm. In another approach, the rocker and the hydraulic lash adjuster are secured together with a pin. The pin may be inserted through both the ball plunger of the hydraulic lash adjuster and the rocker arm. Like the clip approach, because the pin is a separate part, there may be extra cost associated with adding the pin to the existing hydraulic lash adjuster and rocker arm assembly. Moreover, there may be issues concerning service, packaging or robustness of the design that may make the pin approach less desirable.
Therefore, there exists a need to provide a robust and cost effective retention device between the hydraulic lash adjuster and the rocker arm to retain the ball plunger within the rocker arm.